1. Field of the Invention
This invention relates to communication method, communication apparatus, transmitting apparatus, receiving apparatus, communication system, and memory medium. For example, this invention relates to communicating moving picture data through a transmission channel.
2. Description of the Related Art
In recent years, with the spread of personal computers, the use of network, internet and modem communications has increased dramatically, for transmitting various kinds of information.
For example, it is possible for pictures obtained by video-cameras to be supplied to personal computers and stored as moving picture data. Further, making use of communication software, the moving picture data may be sent to other personal computers and host computers through a network, such as Ethernet or other transmission channel such as by modems.
There are difficulties, however, when the above-mentioned image data is transmitted by known communication methods.
First, a bit rate of transmission is very high when moving picture is sent from video-cameras to personal computers, owing to the large amount of data for moving pictures.
For example, consider a case where a single frame of a moving picture has 640 pixels in a horizontal direction and 480 pixels in a vertical direction and has 8 bits for each of R, G, B. If the moving picture is transmitted at the rate of 30 frames per second, the transmission bit rate is 640xc3x97480xc3x9730xc3x973xc3x978=221184000 bit. That is about 220M bit/s.
When a moving picture data of such a high bit rate is transmitted, the loads at the sender side, the transmission channel, and the receiver side become very large. Therefore, in the prior art, when moving picture data is transmitted, transmission capability (bandwidth) of the transmission channel is monopolized by the transmission. Then the number of communications which can occur over the channel at the same time decreases. Other communications are also impeded.
Also, at the receiver side, the personal computer uses most of its capabilities in order to receive the moving picture data, and can not conduct other calculations. Particularly, in order to confirm the received moving picture data, sometimes it is reduced and displayed. According to the prior art, even for confirmation by display on a monitor, the whole moving picture data is transmitted and the load of the receiver side remains heavy.
In order to solve the above-mentioned problem, there are known communication methods which compress the picture, reduce the resolution and/or reduce the frame rate. However, according to these methods, if the received picture is enlarged for display at the receiver side, the picture quality is not good.
Therefore, this invention was made in order to address the above-mentioned shortcomings, and its purpose is to provide communication method, communication device, transmitting device, receiving device, communication system, and memory medium which can take high quality pictures and communicate efficiently.
Especially, it is an object of the present invention to provide an efficient transmission of moving picture data.
In one aspect, the present invention involves communication in which moving picture data is sent from a transmitter to a receiver side through a transmission channel, characterized by the transmitter side sending the moving picture data at a resolution and/or frame rate determined based on an instruction from the receiver side. Preferably, the image data is arranged hierarchically, and is transmitted at a level in the hierarchy determined based on the instruction.
More concretely, the communication between a transmitter side which produces digital moving picture data and a receiving side which receives digital moving picture data through a transmission channel and displays an image based on the data, involves notification of the resolution or frame rate, which is set at the receiving side, to the transmitter side; and supply of the moving picture data to the receiver side by the transmitter side. The resolution and frame rate of the moving picture data is obtained from hierarchically arranged image data based on the notification. Preferably, the transmitter side transmits a part of the hierarchical moving picture data which includes a layer corresponding to the notification instruction from said receiver side. The receiver side may instruct either the resolution or frame rate, or both, to the transmitter side. The transmitter side transmits the moving picture data obtained from an object. The transmitter side may also transmit moving picture data of a kind selected from among plural kinds based on the instruction from the receiver side. At the receiver side, an image is displayed based on the moving picture data from the transmitter side.
In another aspect, the present invention involves communication of moving picture data sent from a transmitter to a receiver side through a transmission channel, characterized by the transmitter side sending the moving picture data at a frame rate determined based on an instruction from the receiver side.
More concretely, the communication between a transmitter side which produces digital moving picture data and a receiving side which receives digital moving picture data through a transmission channel and displays an image based on the data, involves notification of the frame rate, which is set at said receiving side, to the transmitter side; and supply of the moving picture data to the receiver side by the transmitter side. The frame rate of the moving picture data is obtained based on the notification. The moving picture data is preferably arranged hierarchically. Preferably, the transmitter side transmits a part of the hierarchical moving picture data which includes a layer corresponding to the notification instruction from the receiver side. The receiver side may instruct either the resolution or frame rate, or both, to the transmitter side. The transmitter side transmits the moving picture data obtained from an object. The transmitter side may also transmit a sequence of the moving picture data whose identity is selected from among plural different sequences based on the instruction from the receiver side. At the receiver side an image is displayed based on the moving picture data from the transmitter side.
The present invention can be applied to a transmitter side only and also a receiver side only.